1. Field of the Invention
There is a continued interest in the development of novel microbicides which do not have adverse effects on the host, but have high potency against an undesirable pathogen or other microorganism. One area of interest in locating compounds which are microbicidally active are naturally occurring compounds which a host uses in its natural defense. The function of alveolar macrophages in host defense is well documented and numerous reports have been made describing their microbicidal proficiency. See particularly Hocking and Golde, N. Engl. J. Med. (1979) 301:580-587, 639-645. However, relatively little is known concerning the microbicidal mechanisms used by the alveolar macrophages. Rabbit granulocytes have been shown to contain microbicidal lysosomal cationic proteins, certain of which kill microorganisms. As macrophages and granulocytes are thought to arise from a common stem cell and as these cells contain certain constituents in common (e.g. lysozyme), alveolar macrophages appear to be a potential source of compounds having microbicidal activity.
In order for naturally occurring compositions to be useful, there are many criteria. If one is to synthesize an oligopeptide, it is desirable that the number of amino acid units be relatively small. While hybrid DNA technology offers an opportunity to make large proteins, where a microbicidal protein is of interest, the toxic effect of the product on the host evidently creates difficulties in its economic synthesis. Secondly, the microbicidal compound should be independently active and not require the presence of a number of other materials for its activity. Where only a mixture of materials have the microbicidal activity, formulation problems can become severe. Thirdly, one is concerned with the environment in which the naturally occurring compound is active, that is, whether the naturally occurring compound can be formulated in such a way as to be acceptable to the host to be protected from the invading microorganism. Furthermore, by determining the amino acid composition and specific sequence, the peptide may be varied to enhance such properties as stability to degradation, biocidal activity, spectrum activity, and the like. Compounds having biocidal activity against a wide variety of microorganism are particularly important where there is no adverse effect on the host.
2. Description of the Prior Art
Zeya and Spitznagel, J. Bacteriology (1966) 91:755-762 describe cationic proteins of polymorphonuclear leukocyte lysosomes from guinea pigs. Zeya and Spitznagel, Science (1966) 154:1049-1051, describe the antimicrobial specificity of leukocyte lysosomal cationic proteins. Zeya and Spitznagel, J. of Exp. Med. (1968) 127:927-941, describe arginine-rich proteins of polymorphonuclear leukocyte lysosomes from rabbits. Patterson-Delafield et al., Infection and Immunity (1980) 30:180-192, report the isolation in impure form of microbicidal cationic proteins from rabbit alveolar macrophages. Patterson-Delafield et al., Infection and Immunity (1981) 31:723-731 (published Jan. 23, 1981) reports amino acid composition and functional attributes of impure microbicidal cationic proteins from rabbit alveolar macrophages. See also the references cited therein.